The present invention generally relates to global navigation satellite systems (GNSS), and more particularly relates to differential GPS (DGPS) and corrected position solutions, and even more particularly relates to a system and method for communicating differential GNSS pseudo range correction data together with satellite health information to remote aircraft, located beyond the range of VHF data link communications.
In the past, designers of avionics navigation systems have endeavored to provide systems with improved abilities to more precisely make location determinations using GPS satellites. One widely accepted approach to enhancing positional resolution for GPS receivers has been the use of differential. GPS, which involves using a GPS receiver located at a known fixed location to generate pseudo range correction data, which then is provided to mobile receivers via a data link connection, where it is used to enhance the position determination abilities of the mobile receiver. This method is used widely in commercial airports throughout the world. Another method of improving GPS position determinations is for the airborne receiver to receive and use information relative to the health or status of improperly operating GPS satellites.
Trans-oceanic flights are presently spaced about 120 nautical miles apart in line, and fly in a grid system with lanes approximately 60 nautical miles apart to assure positive aircraft separation. Congestion and/or delays are possible owing to the limited number of available routes and the separation between aircraft for safety. Unfavorable winds and turbulence often limit these available routes even further, thereby increasing the potential for congestion and delays. Normal inertial reference systems are typically subject to drift over time and, therefore, would be incapable of providing a high integrity source of position reference throughout an extended flight. Differential GNSS, as well as satellite health and satellite integrity information, could be extremely useful in safely packing more aircraft in these trans-oceanic routes. Trans-oceanic aircraft typically report their locations derived from inertial navigation systems during trans-oceanic flights. Differential GNSS and satellite integrity data are not generally available on trans-oceanic flights, because the data link radios most typically used for such information are VHF radios, with a range of approximately 200 N miles.
Consequently, there exists a need for improvement in systems and methods for controlling trans-oceanic air traffic and for reporting pseudo range correction and providing satellite integrity data to aircraft on trans-oceanic routes.
It is an object of the present invention to efficiently and safely control air traffic for trans-oceanic flights.
It is another object of the present invention to decrease the minimum separation distance between aircraft on trans-oceanic flights.
It is a feature of the present invention to utilize an HF broadcast network of coastal and island-based differential GPS ground stations.
It is an advantage of the present invention to better deliver to trans-oceanic flights both pseudo range correction data being generated by various DGPS stations, as well as satellite integrity information.
The present invention is an apparatus and method for monitoring and reporting pseudo range correction data and satellite integrity information for GPS receivers used on trans-oceanic flights, which is designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features and achieve the already articulated advantages. The present invention is carried out in a xe2x80x9cVHF data link-less systemxe2x80x9d in a sense that the range limitations generally associated with VHF communication have been greatly reduced.
Accordingly, the present invention is a system and method for monitoring and reporting satellite integrity and pseudo range correction data to trans-oceanic GNSS receivers, where the system and method involves using a network of numerous coastal and island-based HF transmitters operating on a set of common frequencies and which use multiplexing.